Paleoarchean World

Scientists in 2002 were convinced they had found evidence that a gigantic meteorite, twice as big as the one which is believed to have wiped out the dinosaurs, collided with Earth billions of years ago.

A report published in the Science journal claimed that deposits of the rock were found in South Africa and Australia. The asteroid, twenty kilometres wide, is believed to have hit the planet with such force that it would have generated tidal waves kilometres high, with the bottom of the ocean being torn up.

Researchers from Stanford University in California and Louisiana State University stated that the cataclysmic event happened about 3.4 billion years ago, before continents were formed and when only bacteria existed. It is not known exactly where the giant meteorite hit as the scientists had not yet located a crater which would have been left by the impact.

Evolution altered

The report said the rock probably came from the asteroid belt between Mars and Jupiter. Researcher Gary Byerly said the object was likely to have been part of a shower of meteorites, some as wide as fifty kilometres.

The impacts were very large, changing the course of evolution on Earth. The report did not say what changes the impact may have affected. There isn't a big extinction event which can be identified which is as cut-and-dried as the extinction of the dinosaurs, according to report co-author, Donald Lowe.

'Incredible tidal waves'

Mr Lowe said it would have taken the rock less than two seconds to pass through the ocean and slam into the sea bed. That impact would generate enormous waves kilometres high which would spread out from the impact site, sweeping across the ocean, and producing incredible tidal waves - causing a tremendous amount of erosion on the microcontinents and tearing up the bottom of the ocean.

Geologists found traces of the meteorite in South Africa's Barberton greenstone belt and Pilbara block in western Australia. The sites contain rocks which were formed more than three billion years ago and which contain information dating back to the beginning of the solar system.

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